Looks like he meant Kasserine, Bizerte and Gafsa. The above website states "On 24 April, Company B of the 20th Engineers was attached to the Free French Corps Franc d'Afrique and conducted the regiment's first assault. The attack went well." Pretty much in line with what his letter says.
I have to wonder since he was wounded in early June whether maybe he was wounded while assisting the removal of mines and such which is what they did following the German surrender in North Africa. I am inclined to believe that maybe he never got back to the unit following his being wounded and was later assigned to another Engineer unit... the 292nd. No evidence for this as of yet.
Gary
Gary, I believe you're 100% correct that the 20th Engineers was the probable unit that my dad was attached to prior to the 292nd. The website link you sent even mentions the 20th guarding President Roosevelt just as my father wrote about in his letter to his mom. And, it's entirely possible that he was wounded clearing mines. Here's the quote, "although the fighting was over, the bloody days for the 20th Engineers were just beginning. They moved into the Sedjenae Valley and began removal of the great minefields. Almost every day had its accident, with a cost of 7 officers and 19 men dead and many more wounded, as the engineers removed over 200,000 German mines".
Thanks so much for your help. I can't wait to share this news with my sister.